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PythonHow to make a multiplication in Python>>> 2+3*414How to print variables in python>>> name = “Andrew”>>> nameAndrewHow to concatenate and print>>> print “Hello”, nameHello AndrewHow to create a list>>> names = [“Ben”,”Chen”,”Yaqin”]How to get the length of a list>>> len(names)3How to get an item from the list>>> names[0]‘Ben’How to get an item from the list using negative values>>> names[-1]‘Yaqin’How to use slice to get substring>>> smiles=”C(=N)(N)N.C(=O)(O)O”>>> smiles[1:5](=N)>>> smiles[10:-4]C(=O)How to find the location of an element>>> smiles.find(“(O”))15>>> smiles.find(“.”)9>>> smiles.find(“.”,10)-1 #nt found>>> smiles.split(“.”)[‘C(=N)(N)N’,’C(=O)(O)O’]How to check if a string is inside another if “Br” in “Brother”: print “contains brother”Remove whitespace like chomp>>> line ‘ This is a comment \n”>>> line.strip()‘This is a comment line’Check if a string starts with>>> email = ‘ceorge@’>>> email.startswith(“c”)TrueCheck if string ends with>>> email = ‘ceorge@’>>> email.startswith(“m”)FalseTurns list into string>>> names =[“Ben”,”Chen”,”Yaqin”]>>> “,” .join(names)‘Ben , Chen, Yaqin’Turn a string into upper case >>> “chen”.upper()CHENChange the char of a string>>> s = “andrew”>>> s[0] = “A” #Doesn’t work>>> s = “A” + s[1:]>>> sAndrewAppend element to a list >>> ids = [“9pti”,”2plv”,”1crn”]>>> ids.append(“1alm”)>>> ids[‘9pti’,’2plv,’1crn’,’1alm’]Delete element from list>>> del ids[0]>>> ids[‘2plv’,’1crn’,’1alm’]Sort elements from list>>> ids.sort()>>> ids[‘1alm’,’1crn’,’2plv’]Reverse elements from list>>> ids.reverse()>>> ids[‘2plv’,’1crn’,’1alm’]Insert element to list at a specific location>>> ids.insert(0,”9pti”)>>> ids[‘9pti,’2plv’,’1crn’,’1alm’]Zipping lists together>>> names[‘ben’,’chen’,’yaqin’]>>> gender = [0,0,1]>>> zip(names, gender)[(‘ben,0),(‘chen’,0),(‘yaqin,1)]How to create a dictionary (hash) in pythonsymbol_to_name = {“H”: “Hydrogen”,“He”: “Helium”,“Li”: “Lithium”,“C”: “Carbon”,“O”: “Oxygen”,“N”: “Nitrogen”}How to get a value of a given key of a dictionary>>> Symbol_to_name[“C”]‘carbon’How to check if a value of a given key of a dictionary exists>>> “O” in symbol_to_nameTrue>>> “U” in symbol_to_nameFalseHow to list all the keys of a given dictionary>>> symbol_to_name.keys()[‘C’,’H’,’O’,’N’,’Li’,’He]How to list all the values of a given dictionary>>> symbol_to_name.values()[‘carbon’, ‘hydrogen’,’oxygen’,’nitrogen’,’lithium’,’helium’]How to update a value from a given dictionary>>> symbol_to_name.update({“P”:”phosphorous”,”S”: “sulfut”})How to print keys and values of a given dictionary>>> symbol_to_name.items()[(‘C’, ‘carbon’),( ‘H’, ‘hydrogen’),(‘O’,’oxygen’),(’N’, nitrogen’),(‘L’, ’lithium’),(‘H’, ’helium’)]How to delete a key of a given dictionary del symbol_to_name[‘C’][( ‘H’, ‘hydrogen’),(‘O’,’oxygen’),(’N’, nitrogen’),(‘L’, ’lithium’),(‘H’, ’helium’)]How to use bool in python>>> smiles =”Hello world!”>>> bool(smiles)True>>> not bool(smiles)FalseHow to use if in python>>> if not smiles print “The SMILES string is empty”How to use elif in pythonMode =”absolute”If mode = “canonical”: smiles = “canonical”elif mode ==” simoeric”:else:do it.>>> smiles‘absolute’How to use For in python>>> names = [“Ben”,”Chen”,”Yaqin”]>>> for ame in names: print nameBenChenYaqinHow to assign tuple in for loops Data = [ (“C20H2003”,”308.371”),(“C20H200k”,”316.393”),(“C20H200i”,”416.6”)]for (formula, mw) in data: print “The molecular weight of %s is %s” % (formula, mw)The molecular weight of C20H2003 is 308.371.The molecular weight of C20H200k is 316.393.The molecular weight of C20H200i is 416. 6.Break, continue Break: stop the for loopContinue: stop the current for loop and restartHow to use range>>> range(5)[0,1,2,3,4]range(5,10)[5,6,7,8,9]range(0,10,2)[0,2,4,6,8]How to read a file>>> f = open(“names.txt”)>>> f.readline()Yaqin\nHow to create file output in pythonInput_file = open(“in.txt”)Output_file = open(“out.txt,”w”)for line in input_file: output_file.write(line)Common file read/write:“w”: write mode“a”: append mode“wb”: write in binary”“r”: read mode (default)“rb”: “read in binary”“U” = “read files with Unix”Math:>>> import math>>> math.pi3.14234234234234>>> math.cos(0)1.0>>> math.cos(math.pi)-1.0>>> dir(math)[‘doc’os…..]>>> help(math)>>> help (math.cos) ................
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